Lesson 1 covered the predictive (waterfall) lifecycle: fix the full scope and plan upfront — a good fit when both requirements and technology are certain. But software and product work is complex, and requirements keep changing; getting everything right upfront just isn't realistic.

Scrum's answer is empirical process control: use short iterations (Sprints) to deliver a small usable increment each time, inspect the feedback, then adapt the next step — turning 'one all-in bet' into 'many small corrections,' which lowers risk and the cost of rework.

That is exactly the consensus 17 software pioneers reached in the 2001 Manifesto for Agile Software Development. It establishes four values:

- Individuals and interactions over processes and tools
- Working software over comprehensive documentation
- Customer collaboration over contract negotiation
- Responding to change over following a plan

Behind the manifesto are 12 principles, for example: working software is the primary measure of progress, welcome changing requirements, deliver frequently, business people and developers work together daily, and maintain a sustainable pace.